they turned on the lights for a massive public art installation that illuminates the san francisco oakland bay bridge. john blackstone spoke with the artist. >> reporter: the lights moving poetically across a two-mile span across the oakland bay bridge are the creation of artist nathan villarreal. on his laptop he put the latest touches that transforms the bridge into a light sculpture. >> this is a unique opportunity. 50 million people will see this over two years. it's something anyone can see and engage with. >> reporter: electricians spent four months in the wind and the cold installing 25,000 l.e.d. lights, each individually programmed to a fiberoptic network. villarreal then began sculptoring the light into patterns he says will never look exactly the same. it changes constantly. how do you do that? >> well, using software. there are sequences which will be displayed in random order in random amount of time. some may recognize the same passage but never in the same order or at the same time. all the motion factors into my creation. water, birds, it's abstract and open-ended, but you